The present invention relates to a system for rapidly changing the clamping jaws on a machine-tool, which may be used for clamping the workpiece to the clamped not only from the inside but also from the outside, for use in repetitive and successive machining operations from the outside or inside the workpieces.
In French Patent Application 85/10958 of Jul. 17, 1985 (corresponding to U.S. Pat. No. 4,763,906), the Applicant described a system for rapidly changing the clamping jaws on a machine tool, comprising self-locking means for locking the jaws M on the jaw-holder P. The self-locking means is formed essentially by a locking element 1 having a base 1.sub.1 on abutment face 1.sub.10 of which said jaw M rests in the locked position and a bearing portion 1.sub.2 for the jaw M, a bearing face 1.sub.20 of bearing portion 1.sub.2 is slanted through an angle .alpha. with respect to a horizontal plane perpendicular to the plane vertical to said face 1.sub.10 of said base 1.sub.1 for cooperating in the locked position with a corresponding bearing face M.sub.20 of the jaw M on the one hand and, on the other hand, by at least one assembly 2 for maintaining said jaw in the locked position. One of the ends 2.sub.10 of a mobile member 2.sub.1 of said assembly 2 has at least one pushing face 2.sub.100 slanted through an angle .beta. with respect to a horizontal plane perpendicular to the plane vertical to said face 1.sub.10 of said base 1.sub.1 for cooperating, in the locked position, with a corresponding bearing face M.sub.20 of the jaw M, said angles .alpha. and .beta. being open in the same direction, said angle .alpha. being greater than said angle .beta.. The assembly 2 further comprises means 2.sub.1, 2.sub.2 for unblocking ande unlocking said jaw M (see FIG. 1).
The angle .alpha. is 1.4 to 2 times the angle .beta. and the difference between the angles .alpha.-.beta. is of the order of 7.degree. to 10.degree.. EQU .alpha.=1.4.div.2;.alpha.-.beta.:7.degree..div.10.degree.
The size of angle .alpha. is preferably from 15.degree. to 30.degree. and that of angle .beta. is preferably from 7.degree. to 20.degree..
The device described in that patent does not allow the jaw to be used from clamping from the outside and/or from the inside of the workpiece to be machined thus requiring the jaw-holder to be changed and/or the jaws for each machining mode. The result is a considerable loss of time, complication due to the multiplicity of jaw-holders and jaws required, and a relatively high production cost.
The object of the present invention is to overcome these drawbacks.